package udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {

    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器开启");
        int i = 1;
        while (i == 0) {
            DatagramPacket requestPacket
                    = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData()
                    ,0,requestPacket.getLength());
            String response = process(request);

            DatagramPacket responsePacket = new DatagramPacket(
                    response.getBytes(),
                    response.getBytes().length,
                    requestPacket.getSocketAddress()
            );

            socket.send(responsePacket);
        }

        while (true) {
            DatagramPacket requestPacket =
                    new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData()
                    ,requestPacket.getLength());
            String response = process(request);
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),
                    response.getBytes().length,
                    requestPacket.getSocketAddress());
            System.out.printf("[%s %d] [req %s res %s]",requestPacket.getAddress(),
                    requestPacket.getPort(),request,response);
        }
    }

    private String process(String request) {
        return request;
    }
}
